Phenotypic identification and development of distinct microvascular compartments in the postnatal mouse spleen

In this paper we report the development of the sinus network of mouse spleen during the first postnatal month as studied with a set of new rat monoclonal antibodies (mAbs) against mouse splenic endothelial cell subpopulations. One of the new mAbs (IBL-7/1) also stained B-cell lineage cells in the spleen shortly after the birth as confirmed by three-color flow cytometry. This B-cell staining in the primordial follicles vanished by the fourth postnatal week, so that the expression of IBL-7/1 antigen was restricted to the marginal sinus endothelium and some red pulp sinuses and a minor B-cell subset in the spleen, presumably distinct from the follicular B-cell compartment. The other mAb (IBL-9/2) selectively labeled the sinusoids of the deeper part of the red pulp, without any reactivity against hemopoietic cells. The IBL-9/2-reactive cells in newborns appeared as isolated elements throughout spleen, and during the segregation of white and red pulps they formed an extensive network in the red pulp outside the marginal zone. Double-labeling immunofluorescence revealed that most of these sinusoids also stained weakly with IBL-7/1 mAb, whereas the strongly IBL-7/1-positive vessels of this region were IBL-9/2 negative. Neither of these mAbs reacted with the central artery. The comparative phenotypic analysis of the various vascular segments indicates that the splenic sinusoids of the marginal zone and red pulp, respectively, are lined with a heterogeneous array of endothelium. For the precise identification, isolation, and characterization of the possible homing function of these endothelium subsets these region-specific mAbs may be of potential value.

Electron microscopic localization of factor-VIII-related antigen in adult human blood vessels

We have localized factor-VIII-related antigen, using immunofluorescence and electron microscopy, in adult human blood vessels. In addition to its presence in endothelial cells, the antigen was localized within subendothelium and the layers of elastic lamina closest to the lumen. Also, we provide the first morphological evidence that factor-VIII-related antigen is associated with collagen fibrils within the vessel wall. These studies suggest that this subendothelial factor-VIII-related antigen may play a role in the adhesion of platelets to subendothelial components following endothelial injury.

Quantitation of B and T lymphocytes in guinea pigs with evidence for a release of both cell types from the spleen into the blood

B and T lymphocytes were quantitated in lymphoid organs and in blood of young normal guinea pigs by the use of EAC rosettes and rabbit erythrocyte (RE) rosettes as markers. Special attention was focused on the release of B and T cells from the spleen, estimated from the difference between the content of B and T cells in splenic efferent and afferent blood. The following frequencies of resette-forming cells (RFC) were found. Thymus: 0.3% EAC- and 88% RE-RFC; spleen: 44% EAC- and 46% RE-RFC; lymph nodes: 13% EAC- and 39% RE-RFC; arterial blood: 13% EAC- and 42% RE-RFC, and bone marrow: 2% EAC- and 7% RE-RFC. A fairly large number of cells in the lymph nodes and blood could not be identified by any of the two markers. Some possible explanations for this are discussed. The content of both EAC- and RE-RFC in splenic efferent blood significantly exceeded that in the afferent blood, indicating a release of both B and T cells from the spleen into the blood. The possibility of a release of a third type of mononuclear cell cannot be excluded from the present results.

Influence of adrenaline on the dissemination of antibody-producing cells from the spleen

Plaque-forming cells (PFC) and rosette-forming cells (RFC) were quantificated in splenic venous and splenic arterial blood and in spleen suspensions of guinea-pigs during a secondary immune response to sheep red blood cells (SRBC). The splenic veno-arterial differences in content of PFC and RFC were determined, indicating whether there had been a release of such cells from the spleen into the blood. The effect of an intracardial injection of adrenaline on the release of immune lymphocytes was investigated. In immunized control animals a splenic release of antigen-binding and antibody-forming cells was found, the release being restricted to the peak of the immune response in the spleen. However, after exogenous adrenaline a considerably increased release of both antigen-binding and antibody-forming cells occurred during a longer period of the immune response. Thus, adrenaline caused an enormous release of PFC from the spleen into the blood on day 4 of the secondary immune response, resulting in a diminished number of PFC remaining in the spleen after the treatment. A physiological significance of an adrenaline-induced dissemination of immune lymphocytes in the body during an immune response to a severe infectious disease is suggested.

A comparative immunohistochemical study of splenic arterial hyalinosis in health and disease

Hyaline deposits in arterioles and arteries of spleen were studied immunohistochemically. Hyaline lesions in arteriosclerotic heart disease were characterized by significant deposits of IgG, IgM, beta1C-beta 1A-globulins and beta-lipoproteins. These corresponded to histochemically stained deposits of acid mucopolysaccharides and microscopic areas of musculoelastic tissue damage in the hyaline masses. While, in young adults and a few other cases of other diseases, an occasional granular to linear deposit of IgG, IgM, beta1C-beta 1A-globulin and beta-lipoprotein was noted, no localization of IgA, rabbit antihuman fibrin and rabbit antihuman fibrinogen was seen. A variety of other histochemical staining reactions were found to be negative. These findings suggest that: a) hyaline deposits in splenic arterioles and arteries occur with greater severity in patients with hypertensive and arteriosclerotic heart disease; b) a possible abnormality related to filtration defects in arteries and arterioles, resulting in the trapping of plasma proteins, appears likely; c) increased localization of acid mucopolysaccharides and destruction of musculoelastic tissue is not an uncommon feature in hyaline masses; d) fibrin is not a component of these deposits and e) further study of other organs is necesary to observe the composition of hyaline in arterioles and arteries.